Genetic Causes of Intellectual Disabilities: Angelman Syndrome
Angelman syndrome was first identified in 1965 by Harold Angelman. The syndrome is chromosomal in nature. It results in neurological problems. This genetic disorder involves the absence or inactivity of a certain group of genes. These genes control ubiquitin; a protein present on chromosome 15q11-13. The abnormal chromosome is typically inherited. However, in some cases it's caused by spontaneous mutation.
The severity of the symptoms varies. It depends on which genes are mutated and how badly they are damaged. Physical traits of Angelman syndrome are not easy to spot. They include a flat-shaped head and a protruding tongue. The circumference of the head is also smaller than average.
Infants with Angelman syndrome appear normal. The first signs are feeding problems that begin during the first two months of life. By six to twelve months, delays in speech are evident. Movement and balance disorders interfere with the child's development. By age three, the child may have seizures.
The condition is marked by several developmental problems. These include problems with communication, walking, and standing. Communication problems are so severe that they may never speak. Many people with this disorder are hyperactive. They have trouble controlling body movements. They often exhibit abrupt, jerking motions, and a stiff posture. Excessive and inappropriate laughter is a telltale sign.
The actual number of cases of Angelman syndrome is unknown. Some estimates are 1 in 15,000 babies have Angelman syndrome. Others estimate 1 in 30,000.
Supportive rehabilitation for Angelman syndrome is helpful. Children are taught cause and effect relationships, and communication skills. Physical and occupational therapies address erratic movements. Speech therapy is essential.